The present invention is directed to a full-roll electronic keyboard system in which an electronic keyboard is connected to an encoder which outputs a multi-bit code such as the well known 7 bit code such as the well known 7 bit ASCII code for each key actuation, and more particularly, to a keyboard circuit for increasing the number of shift keys that are available on a keyboard.
Present electronic keyboards are normally constructed with a predetermined number of shift keys for use in shifting the coded output of associated control keys between the upper and lower case. It has been found that in some business situations, it would be desirable to increase the number of shift keys on the keyboard so as to provide more flexibility in its operation and to better meet the needs of its application. Prior electronic keyboards with shift key capabilities have been constructed in a manner which prevents the addition of shift keys to the keyboard without requiring a new keyboard. Examples of this type of keyboard are found in U.S. Pat. Nos. 3,569,991 and 3,623,588, in which operation of the shift key changes individual code bits of the character key depressed thereby selecting one of two characters represented by the character key depressed. It is therefore a principal object of this invention to provide a circuit for use in wiring a key in a full rollover keyboard for increasing the number of shift keys in the keyboard. It is a further object of this invention to provide circuitry for an electronic keyboard for increasing the number of shift keys on the keyboard without modifying the key structure of the keyboard.